Surges are the Overlooked Storm Threat — But Not for Much Longer

Efforts are under way to improve storm surge warnings and demystify the nature of these events to the public.

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Storm surges are a coastal threat that few taxpayers understand. A surge strikes when a storm causes seawater to rise above the normal predicted tide level. The surge itself consists of extra water that’s been added on top of the tide, and the combination of the two bodies of liquid can spell doom for coastal residents.

Hurricane Katrina, for example, killed more than 1,800 people in 2005, and the National Hurricane Center attributes many of those deaths to the resultant storm surge. Surge flooding of about 25 to 28 feet above the normal tide level struck the Gulf Coast and caused an estimated $75 billion in damage in the New Orleans area, the costliest hurricane on record.

But according to some of America’s most prominent weather experts, storm surges are often overshadowed in the public consciousness by the disasters that create them.

“People by their very nature think wind first. You hear ‘hurricane,’ you think wind. They’re not thinking water,” said Jamie Rhome, the National Hurricane Center’s team lead on storm surges.

“A 100-mile-an-hour wind, 150-mile-an-hour wind — people understand wind, but when you start talking about storm surge, we start using terms like ‘above ground level’ [and] ‘base elevation,’” Koon said. “It quickly gets complicated and as a result, there’s less conversation about it, simply because it doesn’t register as much.”

Government agencies are working diligently to increase storm surge awareness and education. The National Hurricane Center, a division of the federal government’s National Oceanic and Atmospheric Administration (NOAA), is developing storm surge warnings, separate from hurricane warnings, to be ready by 2015, and Koon said Florida is one of several local governments that is developing strategies to publicize storm surge and evacuation zone information.

Under the Radar

Multiple factors contribute to storm surges, which makes them more mercurial and difficult to predict than the forces that generate them. When wind moves in a cyclone around the eye of a storm, the force pushes water to shore and creates the surge, but the surge’s power depends on the storm’s characteristics, which can vary over the disaster’s duration. These features include the storm’s size, forward speed, angle of approach to the coast and central pressure.

Surges’ destructiveness also depends on the land features they hit. If an area has a shallow continental slope, the storm surge will potentially be greater than if the slope were steep. A shallow slope allows water to more easily wash onto shore, but a steeper slope can create a groove that catches more water than it allows to flow. The Louisiana coastline’s shallow continental shelf can produce a high storm surge, as it did in Katrina’s case, but a storm surge that strikes Miami Beach, Fla., which has a steep continental slope, may be much lower.

Consequently, storm surges don’t always match the severity of their accompanying storms, and sometimes storms don’t bring surges at all. This means that storm surges are often overlooked while the severe weather behind them always receives attention.

“In Florida, you get a lot of hurricanes without storm surge, so it’s not something that people always tie together, or if you do, it’s often such a small storm surge that it doesn’t go very far inland and most people are unaware of it,” Koon said. “You get the occasional giant ones like you did with Katrina, so oftentimes when people think hurricanes, they’re not thinking storm surge because it doesn’t always correlate with that.”

Koon also feels that the media focuses on wind damage more than water damage because wind is easier to observe. Reporters can stand near strong winds, but they can’t stand near 20 feet of water rushing onto shore.

“You get reporters standing there with wind blowing them sideways, but, because they would be dead, you don’t get people standing up saying, ‘Here, the water’s 20 feet higher than it normally has been in this location,’” he explained.

Rhome said that reporters don’t understand water events as well as they do wind events. “Your on-camera TV people; they’re meteorologists comfortable with wind. They’re not oceanographers, so they’re not as comfortable with water,” Rhome said.